In general, a dynamometer is a device for operating as a duty load simulator or for measuring the output power of a power generating device or a mechanical power source such as an electric motor, a gasoline or diesel engine, a gas turbine, etc. The measurement may be made in terms of the rotations per minute of a rotating shaft, the torque, or some other form of the source's output power. The primary function of any dynamometer is to produce a load on the source being tested or a torque that acts on an output shaft in a direction opposite to rotation. That is, the dynamometer acts as a damper.
Electric eddy-current generators, Froude-type water brakes, and perforated disk evaporators are some of the known kinds of dynamometers. These known kinds of dynamometers operate according to various physical principles.
Some known dynamometers utilize fluid friction or momentum exchange of water or other liquid to dissipate mechanical power delivered from a connected mechanical power source (e.g., the crankshaft of an engine to be tested, an axle shaft to be slowed, etc.). These known dynamometers use a rotor operating in a bath or spray of water or other liquid within a stator. In accordance with the first law of thermodynamics regarding conservation of energy, the power dissipated in the liquid is converted to heat within the liquid, and the liquid is heated at a rate proportional to the amount of power being dissipated. The heated liquid is discharged from the dynamometer as hot water and simultaneously replaced by cold water.
In general, each known kind of dynamometer is subject to at least one of the following shortcomings: lack of portability due to low power density (i.e., large size and/or weight), complex or costly external equipment required to operate the dynamometer (e.g., condensing equipment or external liquid cooling equipment), erosion of components due to cavitation, short useful mechanical life of components, and limited power absorption capabilities.